Timepiece designers have always endeavoured to increase the reliability of movements, as a result of reducing the frequency of maintenance operations, while ensuring accurate operation of the timepiece movements.
The lubrication of wheels and pinions and moving components is a difficult problem to resolve. Lengthy tribological testing is required to develop solutions to simplify or even eliminate lubrication.
More specifically, it is sought to achieve lubrication-free operation of escapement mechanisms, by attempting to define pairs of materials in friction having a stable, low coefficient of friction and low wear, and exhibiting excellent resistance over time.
Within the scope of the use of materials in non-lubricated friction contact in the timepiece escapement, recent studies tend to show that micro- or nano-crystalline CVD diamond in friction against itself results in the escapement stopping after a limited operating time. This issue necessitates lubrication followed by regular maintenance in the manner of a conventional steel/ruby escapement.
EP Patent Application No 1233314A1 in the name of DAMASKO discloses an escapement mechanism with a pallet lever and escape wheel, wherein at least one of the contact surfaces is coated with DLC.
EP Patent Application No 0732635A1 in the name of CSEM discloses the manufacture of a micromechanical component, particularly a pallet lever of an escapement, with a friction surface including silicon nitride, in an unspecified composition. This document envisages a pair with a counter-piece?, with improved tribology: this document cites a titanium nitride against titanium carbide pair, or a titanium nitride against silicon carbide pair.